Low-cost manufacture of flexible torque coupling



7 E. s. CHALPIN ET AL 3,346,945

LOWCOST MANUFACTURE OF FLEXIBLE TORQUE COUPLING Original Filed March 27,1964 I5 $heets-$heet l ATTORNEYS FIG. 2

Oct. 17, 1967 E. s. CHALPIN ET AL 3,346,945

LOW-COST MANUFACTURE OF FLEXIBLE TORQUE COUPLING Original Filed March27, 19 4 3 Sheets-Sheet 2 FIG.5

EDWARD S. CHALPIN DAVID E HANSON I N VEN TORS BY M W ATTORNEYS Oct. 17,1987 CHALPlN ET AL 3,346,945

LOW-CO5T MANUFACTURE OF FLEXIBLE TORQUE COUPLING Original Filed March27, 1964 I5 Sheets-Sheet 5 ATTONES United States Fatent Oflfice3,346,945 Patented Oct. 1?, 1967 3,346,945 LOW-COST MANUFAOTURE OFFLEXIBLE TORQUE COUPLING Edward S. Chalpin, Glendora, Calif., and DavidE. Hanson, Brockton, Mass, assignors to Metal Bellows Corporation,Sharon, Mass.

Original application Mar. 27, 1964, Ser. No. 355,376, now Patent No.3,301,007, dated Jan. 31, 1967. Divided and this application Apr. 29,1966, Ser. No. 559,025

4 Claims. (Cl. 29436) This application is a division of application Ser.No. 355,376, filed Mar. 27, 1964, now Patent No. 3,301,007, granted Jan.31, 1967.

This invention relates to a novel low-cost construction for a bellowscoupling and comprehends a method for manufacturing it.

Flexible torque couplings of the present kind are capable oftransferring torque between two shafts that are subject to independent,or differential, lateral and longitudinal motions as well as angulardeflection. One construction for such shaft couplings utilizes bellows.Advantages of the bellows-type flexible torque couplings include theabsence of frictional wear between elements of the coupling, and highflexibility to accommodate lateral, longitudinal, and angularmisalignment. This latter feature allows the coupled shafts to besubstantially misaligned and yet have minimal lateral and bendingstresses.

Moreover, the full symmetry of the bellows around the axis of rotationcan provide a constant speed characteristic. In addition, the bellowselements in such devices may be constructed with suflicient torsionalrigidity to prevent appreciable relative rotational displacement betweenthe coupled shafts. Put another way, the rotational movement of thedriving shaft is precisely communicated to the driven shaft, since thereis no inherent slack or play in the coupling.

However, the use of flexible bellows-type couplings has often beenretarded due to their generally lower strength compared with othertorque couplings of lesser flexibility. Specifically, although thediaphragm or bellows elements of a bellows coupling provide an extremelyhigh strength coupling having remarkably low stress concentrations, theyare subject to failure, particularly when inadvertently damaged by anexternal force.

Another problem with prior bellows-type couplings is their relativelyhigh cost, which precludes their use in applications where cost is aprime consideration.

Accordingly, an object of the present invention is to provide a methodof making a fail-safe torque coupling characterized by high performanceprior to failure and continued operation in the event of failure.

Another object of the invention is to provide a method of making afail-safe flexible torque coupling that has high torsional rigiditytogether with lateral flexibility.

Another object of the invention is to provide a method of making afail-safe flexible torque coupling that is compact and has light weight.The coupling should also have low inertia.

A further object of the invention is to provide a method ofTnaking abellows-type flexible torque coupling having fail-safe operation.

A further object is to provide an improved method of making a flexibleshaft coupling of economical and simplified design.

It is also an object of the invention to provide a method forfabricating metal bellows couplings of the above character at low cost.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combinations of elements, and arrangements of parts which will beexemplified in the constructions hereinafter set forth, and the severalsteps for making these constructions and the relation of one or more ofsuch steps with respect to each of the others, and the scope of theinvention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

FIG. 1 is a side elevation view, partly broken away, of a fail-safeflexible shaft coupling embodying the invention, shown connected betweenmisaligned shafts;

FIG. 2 is an end view, partly broken away, of the coupling of FIG. 1;

FIG. 3 is an end view, similar to FIG. 2, of the coupling of FIG. 1 withthe elements thereof aligned;

FIG. 4 is a longitudinal section of a modified construction for thecoupling of FIG. 1;

FIG. 5 is a side view, partly broken away, of a low cost shaft couplingembodying the invention.

A fail-safe coupling embodying the invention has a primary bellowscoupling unit connecting a driving member with a driven member. Alsoconnected between the two members, which are appropriatelyshaft-receiving hubs, is a secondary coupling unit. The torsionalrigidity of the primary unit maintains the secondary unit disengaged sothat the connection between the hubs has high flexibility, except fortorsional stresses.

In the event that the primary coupling fails, or the torsional rigidityof the primary unit otherwise decreases to allow the hubs to becometorsionally offset, the secondary unit engages and commences to transferthe torsional load between the hubs.

In this manner, the coupling combines the highly desirable operatingcharacteristics of bellows-type flexible torque couplings with highreliability. The invention thus enables bellows-type couplings, withtheir inherent features of relatively silent, lubrication-free andnon-Wearing operation to be used in critical applications where safetyand reliability are prime considerations. One such application is in thesteering mechanism of motor vehicles.

More specifically, as shown in FIGS. 1 and 2, a coupling indicatedgenerally at 50 interconnects shafts 52 and 54. The coupling has aprimary coupling unit indicated generally at 56, connected betweenaxially spaced, shaftreceiving hubs 58 and 60. The primary coupling unit56, in turn, comprises an elongated, rigid cylinder 62 connected betweenbellows 64 and 66 that are connected at their other ends to the hubflanges 58a and a, respectively.

The coupling 50 also has a secondary coupling unit indicated generallyat 68, comprising disengaged sections 70 and 72 connected with the hubs58 and 60, respectively, and disposed coaxially within the cylinder 62of the primary unit. The sections 70 and 72 are adapted to engage eachother and transfer torque between the shafts 52 and 54 in the event theprimary coupling unit 56 fails.

-In the illustrated embodiment, a pair of opposed arcuate lugs 74 and76, integral with the hub 58, form the section 70. The lugs 74 and 76extend axially toward the hub 60 to interleave with an identical pair ofopposed arcuate lugs 78 and 80 (FIG. 2), integral with the hub 60 andforming the coupling section 72.

As best seen in FIG. 3, where the hubs are in alignment, the lugs 74-80are equally spaced around the circumference of a common circle with eachlug of the section 70 between lugs of the section 72 and vice versa.Radially extending surfaces 74a, 76a, 78a and 80a on the lugs arecircumferentially spaced from mating surfaces on adjacent lugs.

The bellows 64, and 66 are preferably of welded metal construction, witha plurality of generally frustro-conical diaphragms as shown. Thediaphragms are rippled with a radial succession of circumferentiallyextending undulations to increase their flexibility and their resistanceto buckling deformation under high torque loads.

The flanges 58a and 60a may be integral with the hubs, as shown, orformed of sheet stock and secured to the hubs as by welding or brazing.The shafts 52 and 54 are secured in the hubs 5S and 60 in a conventionalmanner, e.g., with pins 59 and 61.

It has also been found that the bellows-cylinder and bellows hubconnections are preferably continuous around the entire bellowsperiphery so that the coupling provides constant-speed operation. In theabsence of continuous weld or similar connection, suflicient deformationcan oc cur when the hubs are oflset from each other to cause speedvariations.

During operation, the coupling 50 efficiently transfers torque betweenthe shafts 52 and 54 with relatively quiet and friction free operation.Moreover, the coupling has no noticeable torsional windup and hence itmaintains a substantially fixed relative rotational orientation of theshafts 52 and 54, and the elements of the coupling.

The circumferential spacing between the adjacent lugs of the secondarycoupling unit 68 is SUlfiClCIIt to prevent contact between them as longas the primary unit 56 remains intact. Such contact would decrease thecouplings flexibility and hence its misalignment accommodation, inaddition to producing some noise and wear during operation.

Accordingly, when the shafts 52 and 54 are in the position of maximumlateral misalignment, as shown in FIGS. 1 and 3, the lugs 74 and 76 ofthe coupling section 70 are still disengaged from the lugs78 and 80.However, if the primary coupling unit 56 fails, the adjacent lugs of thetwo couplings section 70 and 72 will undergo relative rotation and thusengage each other and continue to transfer torque between the hubs 58and 60 and the shafts connected thereto. It will also be seen that whenthe secondary coupling unit is brought into action by failure of theprimary unit, the coupling 50 still accommodates misalignment of thecoupled shafts 52 and 54, although not with the same high etficiency andflexibility it had prior to such failure.

The construction of the coupling 50 shown in FIG. 1 provides a highdegree of protection for the relatively fragile bellows 64 and 66, sincethe outer radial dimensions of the cylinder 62 and hub flanges 58a and66a are at least as large as the bellows, and hence shield the bellowsfrom inadvertent damage. Moreover, even with added parts, the couplinghas low inertia and small size.

FIG. 4 shows an alternative construction for the failsafe coupling andcomprises the same elements as the coupling 50. However, in FIG. 4, thebellows 64 and 66 and the hubs 58 and 60 are disposed within thecylinder 62 rather than axially spaced therefrom as in FIG. 1. Further,the coupling of FIG. 4 does not have hub flanges.

In the couplingsdescribed above, the cylinder between the bellows may bereplaced with other shaft-like torquetransferring structures. It shouldalso be noted that the interior of the coupling is vented through a hole63 (FIG. 1) in the cylinder 62 to have the same pressure as theenvironment.

As shown in FIG. 5, the fail-safe features of the invention are alsosuited for use in a single-bellows coupling. A coupling indicatedgenerally at 82 includes a bellows 84 interconnecting axially-spacedcylindrical hubs 86 and 88. The hub 86 has lugs 91) and 92 interleavedwith lugs 94 and 26 of the hub 88.

The bellows 84 preferably comprises a plurality of convolutions 96, eachformed with a pair of rippled frustroconical diaphragms 98 arranged backto back and welded together at their inner rims. The convolutions arejoined by welding together the mating outer rims of adjacent diaphragms.The end diaphragms 98a and 98b have axially extending inner rims 108permanently joined with the 4 hubs 86 and 88, by welding, brazing, or asuitable cement such as an epoxy.

Still considering FIG. 5, the single-bellows coupling 82 may also beconstructed with annular flanges (not shown) on each of the hubs 86 and88 and preferably having a diameter at least as great as the outerdiameter of the bellows 84. Such flanges will largely protect thebellows 84 from inadvertent damage. When protective flanges are thusprovided, the bellows 84 may remain secured to the hubs as shown, orhave its outer end rims secured to the flanges in a manner similar tothat shown in FIG. 1.

FIG. 6 shows a coupling embodying the invention and characterized by alow-cost construction and high performance. The coupling comprises atwo-piece bellows unit 102 interconnecting axially spaced tubular hubs104 and 1%. Two preferably identical cups 188 and constitute the bellowsunit 102. The cup 110 has a cylindrical wall 112 and is bottomed with abellows diaphragm 114. The diaphragm114 has an inner cylindrical rim 116secured to the hub 106-. The cup wall 112 flares out and forms anannular rim 118 that is secured to a mating rim 120 flaring out from thewall .122 of the cup 108. The cup 108 also has a bellows diaphragm 124terminating at its inner edge in a cylindrical rim 126 secured to thehub 104. The cups have vent holes 113 and 123.

As also shown in FIG. 6, the bellows diaphragms 114 and 124 arepreferably rippled with a radial succession of circumferentialundulations. As shown on the diaphragm 114, the radially outermostundulation 114a has a relatively large curvature; that is, a relativelysmall radius of curvature. The curvature of the undulations successivelydecreases in the direction of decreasing radius, so that the innernndulation 1141) has a relatively small curvature. Thus, the axialamplitudeof t-he undulations and the widths thereof in the radialdirection increase in the direction of decreasing radius. This ripplingconstruction with decreasing curvature appears to distribute stressesfairly evenly along the radial dimension of the diaphragm, therebyminimizing stress concentrations.

The diaphragm 114 is also radially bowed along a curve 128, with therippling undulations superimposed on the curve as indicated in greaterdetail in FIG. 6A. It has been found that such bowing of the diaphragmincreases its flexibility, particularly in the axial direction, andincreases the operating life of the bellows unit.

The center of curvature of the curve 128 preferably lies between thewall 112 and the inner rim 116. Thus, the curve is double-valued in theradial direction and has a crest 128a intermediate the inner rim 116 andthe outer wall 112.

The diaphragm 124 is preferably identical to the diaphragm 114 and bowedopposite to the diaphragm 114 along a curve 130 identical to the curve128.

The cups 108 and 110 of the coupling 102 are readily fabricated at lowcost from sheet stock by a conventional drawing operation. Since thecups 108 and 110 are identical, they can be formed with the same dies.The drawing.

operation forms both rims (e.g. 116 and 118) and the diaphragm.Thereafter, the cups are axially positioned on the hubs 104 and 106 andsecured thereto. By way of example, this may be done by seam welding, inwhich a series of spaced axial lines welds 132, shown uniting the rim126 with the hub 104, are rapidly formed about the periphery of therims. One construction for seam welding apparatus utilizes a toothedwheel as the welding electrode. The welding voltage is applied betweenthe hub and the tooth wheel and as the wheel is rolled around the rim126, it draws an are between each tooth of the 1 wheel and the rim toform the line weld. Other welding or brazing techniques canalternatively be used to secure the cups to the hubs. However, we havefound it preferable to accomplish the desired banding by means ofadhesives such as epoxy, which provide uniform stress concentration inthe cups all the Way around the hubs 184 and 1'36.

The rims 118 and 120 of the cups 108 and 110, respectively, are thenjoined together. In the illustrated embodiment, they are rolled andcrimped. Adjacent, circumferentially spaced sections of the abuttingrims are crimped and offset in opposite axial directions, so that theconjoined rims 118 and 120 form an axially undulating path, as shown.This construction, readily performed with conventional equipment,prevents the cups from slipping with respect to each other, even underhigh torque loads.

The coupling structure of FIG. 6 may incorporate a second coupling unitfor fail-safe operation. For this purpose, in the illustratedembodiment, the hubs 104 and 105 are formed with pairs of opposedinterfitting lugs 134 similar to those disclosed above with reference toFIGS. 1, 2 and 3.

The hubs 104 and 106 are fabricated from conventional tube stock and thefail-safe coupling lugs are automatically formed by removing the tubeportions between the lugs on each hub. This operation is readily adaptedto massproduction techniques such as punching, etc.

The shaft-receiving ends of the hubs may be broached to form splines, asshown at 132 on the hub 106, which securely engage shafts fittedtherein.

When the coupling 102 does not have the fail-safe lugs 134, the cups 108and 110 can be very shallow, with short walls 112 and 122.

The high performance, strength, ruggedness and reliability, and the lowcost of the coupling shown in FIG. 6 renders it highly suited for manyapplications, one of which is as a universal connection in a driveshaft.

The invention thus provides a flexible shaft coupling in which thefragile metallic bellows elements are effectively protected from damage.This is accomplished in a simple and ingenious manner by providing anelongated cylinder of sufficient size to extend radially beyond thebellows aflixed thereto. By this arrangement, the cylinder effectivelyabsorbs the impact of accidental blows, thereby preventing damage to thebellows.

The fail-safe bellows shaft couplings described above also provide aremarkably high degree of reliability without interfering with theirhigh misalignment flexibility. Moreover, the low cost and light weightembodiment described above overcomes substantial practical problems thatheretofore have precluded the use of low-noise frictionless andlubrication-free bellows couplings in many machines.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efliciently attained and,since certain changes may be made in carrying out the above methods andin the constructions set forth without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention, which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. A method for fabricating a flexible torque coupling, said methodcomprising the steps of (A) forming a metal sheet into a cup having aflexible diaphram extending radially along the cup bottom and a tubularwall extending axially along the cup wall from the outer periphery ofsaid diaphragm to a first edge,

(B) providing torque-transferring means on each diaphragm radiallyspaced inwardly from its outer periphery,

(C) securing together said first edges of first and second cups disposedin opposition to each other so that said torque-transferring means onsaid two cups are axially spaced apart.

2. The method defined in claim 1 in which said cupforming step formseach of said diaphragms with an axial bow and with radially-spacedundulations.

3. The method defined in claim 1 (A) in which said torque-transferringmeans is formed as a cylindrical shaft-receiving rim, and

(B) further comprising the step of securing first and second hubs insaid shaft-receiving rims of said first and second cups, respectively,prior to securing said cups together.

4. A method for fabricating a fail-safe flexible torque couplingcomprising the steps of (A) forming a metal sheet into a cup having (1)a cylindrical torque-transferring inner rim forming an axially-centeredhole in the cup bottom,

(2) a flexible diaphragm extending radially outwardly from said innerrim, and

(3) a cylindrical cup wall extending axially from the outer periphery ofsaid diaphragm to an annular flange,

(B) forming a tubular hub having at least two arcuate axially-extendinglugs at a first end thereof,

(C) securing said inner cylindrical rim of said cup to said hub to forma cup-hub assembly with said lugs being within the cup wall andextending axially beyond said annular rim, and

(D) securing together said outer annular rims of two cup-hub assemblieswith their lugs interleaved and circumferentially spaced apart.

References Cited UNITED STATES PATENTS 1,471,143 10/1923 Cromwell 64-151,752,106 3/1930 Persons 64-13 1,842,149 1/1932 Clifford 29-454 XR2,069,727 2/1937 Spencer 29-454 XR 3,000,089 9/1961 Baker et al. 29-4363,046,759 7/1962 Deford et al. 64-11 3,099,879 8/1963 Horovitz 29-436FOREIGN PATENTS 923,640 2/ 1955 Germany.

JOHN F. CAMPBELL, Primary Examiner. THOMAS H. EAGER, Examiner,

1. A METHOD FOR FABRICATING A FLEXIBLE TORQUE COUPLING, SAID METHODCOMPRISING THE STEPS OF (A) FORMING A METAL SHEET INTO A CUP HAVING AFLEXIBLE DIAPHRAM EXTENDING RADIALLY ALONG THE CUP BOTTOM AND A TUBULARWALL EXTENDING AXIALLY ALONG THE CUP WALL FROM THE OUTER PERIPHERY OFSAID DIAPHRAGM TO A FIRST EDGE, (B) PROVIDING TORQUE-TRANSFERRING MEANSON EACH DIAPHRAGM RADIALLY SPACED INWARDLY FROM ITS OUTER PERIPHERY,